A friend who wanted to start a home gym asked me if she should get kettlebells instead of dumbbells. This was my take on it:
Kettlebells are awesome. They add an extra dimension to your workouts that you just can't get with dumbbells. Having a handle offset from the weight's center of mass means there is a lot more coordination involved and you're activating a whole slew of stabalizing muscles.
That said, kettlebells can cost 2-3 times what a dumbbell of the same weight will cost. If you have little to no experience with kettlebells, you're not going to get as much out of them to be worth that extra cost. And frankly, you can replicate kettlebell exercises with dumbbells
Therefore, when putting together a home gym, I would recommend using your budget on a larger set of dumbbells with a greater variety of weights than on a few kettlebells.